Vertical wind observation in the tropical upper troposphere by VHF wind profiler: A case study

Yamamoto, Masayuki; Nishi, Noriyuki; Horinouchi, Takeshi; Niwano, Mototaka; Fukao, S.

doi:10.1029/2006rs003538

Cited by 10 publications

(10 citation statements)

References 34 publications

(45 reference statements)

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“…Observations of high frequency waves in the stratosphere have shown a close correspondence with convective clouds (Sato et al, 1995;McLandress et al, 2000;Alexander et al, 2000). Our observations are similar to the events previously reported at the EAR in Indonesia (Dhaka et al, 2005;Yamamoto et al, 2007).…”

Section: Observationssupporting

confidence: 80%

High resolution observations of turbulence in the troposphere and lower stratosphere over Gadanki

Dutta¹,

Kumar²,

Kumar³

et al. 2009

Ann. Geophys.

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Abstract. High resolution (150 m) wind measurements from 13-17 July 2004 by Mesosphere-Stratosphere-Troposphere (MST) radar and 15-16 July 2004 by Lower Atmospheric Wind Profiler (LAWP) have been used to study the time variation of turbulence intensity. Layers of higher turbulence are observed in the lower stratosphere on 15-16 July which give rise to mixing in the region. Enhancement in short-period gravity wave activity and turbulent layers are observed after 22:00 LT which could be due to a dry convection event that occurred at that time. The breakdown of the convectively generated high frequency waves seems to have given rise to the turbulence layers. Wind shear is found to be high above the easterly jet, but very poor correlation is observed between square of wind shear and turbulence parameters in the region. The heights of the turbulent layers in the lower stratosphere do not correlate with levels of minimum Richardson number. A monochromatic inertia gravity wave could be identified during 13-17 July 2004. A non-linear interaction between the waves of different scales as proposed by Hines (1992) might also be responsible for the breakdown and generation of turbulence layers.

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Section: Observationssupporting

confidence: 80%

High resolution observations of turbulence in the troposphere and lower stratosphere over Gadanki

Dutta¹,

Kumar²,

Kumar³

et al. 2009

Ann. Geophys.

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“…Evidence based on the observations using Indian MST radar located at Gadanki (13.5 • N, 77.0 • E) during May-June and Equatorial Atmosphere Radar (EAR) at Kota Tabang (0.2 S, 100.32 E) shows that vertical winds become enhanced when associated with convective activity (Dhaka et al, 2001(Dhaka et al, , 2002(Dhaka et al, , 2006Yamamoto et al, 2007). As a result, adiabatic expansion of air mass at higher levels can lead to cooling.…”

Section: Resultsmentioning

confidence: 99%

Influence of large-scale variations in convective available potential energy (CAPE) and solar cycle over temperature in the tropopause region at Delhi (28.3°N, 77.1°E), Kolkata (22.3°N, 88.2°E), Cochin (10°N, 77°E), and Trivandrum (8.5°N, 77.0°E) using radiosonde during 1980–2005

et al. 2010

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We have shown the relationship between seasonal, annual, and large-scale variations in convective available potential energy (CAPE) and the solar cycle in terms of temperature at the 100-hPa pressure level using daily radiosonde data for the period 1980 • N, 77. • E) and Trivandrum (8.5• N, 77.0 • E), India. In general, there was a tendency for increases in CAPE to be associated with decreases in temperature at the 100-hPa pressure level on all time scales. Decreasing linear trends in temperature were found at Delhi and Kolkata over the period [1990][1991][1992][1993][1994][1995][1996][1997][1998][1999][2000][2001][2002][2003][2004][2005][2006]. Our analysis suggests that the trend towards increasing convective activity in the troposphere leads-at least partly-to the trend towards cooling in the tropopause region. High CAPEs are, in general, associated with high rainfall. The minimum annual temperatures were observed almost simultaneously with enhanced annual CAPE during the northern summer, with a larger anti-correlation (−0.62) over Delhi than at other stations. The influence of the solar cycle on the control of temperature was significant (∼4-5• C) only around 8-10• N. Temperature variations in the upper troposphere are viewed as being jointly controlled by CAPE and the solar cycle, with the respective contribution of each being location-dependent.

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“…The EAR is a 47 MHz clear‐all Doppler radar that can measure vertical winds under both clear and rainy conditions. The EAR data used in this study was averaged over 90 min, with a vertical resolution of 150 m. A typical uncertainty in the vertical wind measurements at the original temporal resolution (about 80 s) is less than 0.1 m s −1 [ Yamamoto et al , 2007].…”

Section: Data Descriptionsmentioning

confidence: 99%

Analysis of the tropical tropopause layer using the Nonhydrostatic Icosahedral Atmospheric Model (NICAM): 2. An experiment under the atmospheric conditions of December 2006 to January 2007

Kubokawa¹,

Fujiwara²,

Nasuno³

et al. 2012

J. Geophys. Res.

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[1] The roles of deep convection and generated waves in the Tropical Tropopause Layer (TTL) are investigated using a global nonhydrostatic model, the Nonhydrostatic Icosahedral Atmospheric Model (NICAM), which runs on the Earth Simulator with a horizontal spacing of 7 km. The model data, which successfully simulated a Madden-Julian Oscillation (MJO) event for the period between 15 December 2006 and 15 January 2007, are analyzed. The frequency of deep convective clouds that reach the TTL is one of the key diagnostics for dehydration and transport. The present results revealed that the proportion of cumulus clouds that penetrate the lapse-rate tropopause and the bottom boundary of the TTL (defined as the lapse rate minimum) is $0.5% and $20%, respectively, in the region between 5 S and 5 N. This result is reasonably consistent with atmospheric observations. Deep convective activity that reaches the TTL was observed over southern Africa, the Indian Ocean, the Indonesian maritime continent, the western Pacific, and southern America. Deep convection over the continents was most active during the local evening period. Over the oceans, high clouds reaching the tropopause were seen over the Indian Ocean and the seas around Java, where two tropical cyclones were generated. Prominent diurnal variations in tropopause temperature associated with deep convection occurred over the Indonesian maritime continent. These diurnal variations were superimposed on large, low-frequency temperature variations associated with equatorial Kelvin waves generated by the MJO convection. Probably because of coarse vertical resolution, temperature variations simulated by the NICAM are larger than those in the real atmosphere. The two tropical cyclones caused relatively large tropopause temperature variations with a cyclone scale ($500 km horizontally). The gravity waves generated by tropical cyclones cause small tropopause temperature variations that extend for 1000 km from the cyclone. We conclude that the Kelvin waves associated with the MJO convection cause the largest amplitude of temperature variations in the TTL and that tropical cyclones and diurnal variations of convective activity have large local impacts on temperature variations in the TTL.

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Vertical wind observation in the tropical upper troposphere by VHF wind profiler: A case study

Cited by 10 publications

References 34 publications

High resolution observations of turbulence in the troposphere and lower stratosphere over Gadanki

High resolution observations of turbulence in the troposphere and lower stratosphere over Gadanki

Influence of large-scale variations in convective available potential energy (CAPE) and solar cycle over temperature in the tropopause region at Delhi (28.3°N, 77.1°E), Kolkata (22.3°N, 88.2°E), Cochin (10°N, 77°E), and Trivandrum (8.5°N, 77.0°E) using radiosonde during 1980–2005

Analysis of the tropical tropopause layer using the Nonhydrostatic Icosahedral Atmospheric Model (NICAM): 2. An experiment under the atmospheric conditions of December 2006 to January 2007

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